1. Field of the Invention
The invention relates to the mounting of an oil cooler to a heat exchanger tank, and more particularly to a structure and method of mounting an oil cooler made of aluminum to a heat exchanger tank made of aluminum.
2. Description of the Related Art
As oil cooler incorporated heat exchangers, the following conventional examples are known. One example is characterized as brazing a heat exchanger tank and an oil cooler together as disclosed in Unexamined Japanese Utility Model Publication No. Sho. 63-17824, and another example is characterized as screwing an oil cooler onto a heat exchanger tank that is made of a synthetic resin so as to be watertight as disclosed in Japanese Utility Model Publication No. Hei. 6-43223.
In the former example, the oil cooler and a core portion of the heat exchanger can be brazed integrally, so that unlike the latter example that involves the steps of mounting the oil cooler inside the heat exchanger tank and assembling a core portion formed of a tube and a fin thereafter, the former example allows an oil cooler incorporated heat exchanger to be not only assembled in a simplified way but also provided in large quantities inexpensively.
FIG. 12 shows the oil cooler incorporated heat exchanger of the former example.
In FIG. 12, reference numeral 1 denotes an oil cooler. The oil cooler 1 has seat portions 3 on both ends thereof, and an oil cooler main body 2 is interposed between the seat portions 3. A stepped mounting surface 4 is formed on each seat portion 3. The stepped mounting surface 4 is engageable with a stepped protruding portion 6 arranged on a tank (usually, the lower tank of a heat exchanger).
The oil cooler 1 is brazed with the stepped surfaces 4 engaged with the stepped protruding portions 6 of the tank 5.
As a result of this construction, the oil cooler 1 can be incorporated into the tank 5.
It may be noted that oil introducing/discharging pipes 7 of the oil cooler 1 are brazed to the stepped protruding portions 6 of the tank 5 while engaged therewith.
However, such conventional oil cooler incorporated heat exchanger requires not only that the stepped mounting surfaces 4 be formed on the seat portions 3 of the oil cooler 1, but also that the stepped protruding portions 6 be formed on the tank 5, which increases the number of machining steps and hence makes the machining operation cumbersome.
In addition, in order to engage the stepped mounting surfaces 4 with the stepped protruding portions 6, high machining accuracies are called for. If a gap is formed between the mounting surface and the protruding portion, the brazing filler metal is not adequately spread over and may, therefore, cause defective brazing.
Further, the stepped mounting surfaces 4 must be kept engaged with the protruding portions 6 at the time of brazing, which makes the brazing operation cumbersome. If the brazing operation is performed with both members poorly engaged, the brazing material is not well spread over, which in turn causes defective brazing.